1. Field of the Invention
This invention relates to a thin board holding device for holding a thin board in a plane state to measure the thickness of the thin board and also to a method of and an apparatus for the thin board thickness measurement on holding a thin board in a plane state.
2. Description of the Related Art
The thickness of a thin board, such as a film-like sheet or a silicon wafer, is usually measured with a micrometer.
To measure the thickness, the thin board is held with one hand, and the micrometer is operated with the other hand. Therefore, when the thin board is inserted into and pushed out from the space between micrometer measurement terminals, the thin board may strike or be distorted between the terminals, and this may result in its breakage.
Therefore, it is difficult to accurately measure the thickness of a thin board, particularly a large diameter and fragile thin board such as a silicon wafer.
FIG. 13 shows a related technique, in which displacement gauges 101 and 102 provided on a frame 100 over and under a thin board 1 under measurement measures the thickness of the thin board 1.
In this system, the displacement gauges 101 and 102 should be such that their relative positions are not varied and that the thin board under measurement can be passed between them. Therefore, the system is inevitably rather elaborated, and a high technical level is necessary.
In addition, in this system it is necessary to move a silicon wafer to measure the thickness thereof at a plurality of designated points, so that greater caution and time are required to prevent breakage of the wafer, thus reducing the production rate and increasing the cost of manufacture. It has been desired to solve this problem.